1. Field of the Invention
The present invention relates to a circuit device.
2. Description of the Related Art
Recently, such a circuit device has been suggested which incorporates both a sensor such as a microphone and an application specific integrated circuit (ASIC).
Such a circuit device can put intelligence in the sensor.
For example, a circuit device with a microphone incorporated as the sensor would be able to realize a voice recognition capability, semantic conversion capability, bi-lingual capability or the like.
For example, the aforementioned circuit device includes those described in Japanese National Publication of International Application No. 2003-508998 and “Stacked Silicon Microphones”, by M. Mullenborn et al., EUROSENSORS, XIV, pp 209-212.
The circuit devices described in these documents implement a sensor and an ASIC on separate chips, in which the flip-chip bonding technology is used to individually implement both the chips on a silicon substrate.
This allows the sensor and the ASIC to be electrically connected with each other via the silicon substrate.
However, the circuit devices configured as described above are manufactured at high costs.
That is, the circuit devices configured as mentioned above are manufactured at high overall costs due to at least three types of costs required for their fabrication. That is, these costs are required for (i) forming a sensor on a first substrate to fabricate a first chip, (ii) forming an ASIC on a second substrate to fabricate a second chip, and (iii) implementing the first and second chips on a silicon substrate carrier.
To address this problem, the sensor and the ASIC may be formed on the same chip.
However, in general, ASICs are preferably isolated from ambient air as much as possible in order to prevent water or moisture from infiltrating therein. In contrast to this, sensors must be exposed to ambient air in order to sense required information.
In this context, there is apprehension that a circuit device having a sensor and an ASIC formed on the same chip may cause the ASIC to be infiltrated with water or moisture from where the sensor is formed.
When water or moisture infiltrates into the ASIC, water molecules (H2O) may spread through the inter-layer dielectric film. This can give rise to corrosion of the conductors and deterioration of circuit components such as transistors, thereby causing the circuit device to be reduced in reliability.